This section provides background information related to the present disclosure which is not necessarily prior art.
Ultrasonic energy has been shown to be a useful tool in a wide variety of applications from very low power medical diagnostics through high intensity processes which change the state of materials. Joining of plastics, specifically thermo plastics, is a particularly useful application of this technology. Ultrasonic welding of thermoplastics has been demonstrated to eliminate most, if not all, of these problems. In fact, ultrasonic welding of plastics has become the process of choice by informed design and manufacturing engineers. The number of applications and reduced operating expenses have led to wide use of ultrasonic welding for thermoplastic applications.
Since the first ultrasonic welding machine for plastics was developed in 1960, there have been significant technological advances which now make the process a practical production tool. Early power supplies, employing vacuum tube technology, could not produce high power levels of ultrasonic energy and were inefficient and expensive. Early work was limited to research and development which showed the promise of the process and spurred further technical development. Today, ultrasonic energy in general is a well established tool of industry having applications in nondestructive testing, industrial ultrasonic cleaning, ultrasonic plastic joining and ultrasonic metal welding. Ultrasonic plastic welding has much to offer the user including speed, efficiency, excellent weld quality, elimination of consumables, long tool life and the ability to be automated.
Generally, ultrasonic energy is mechanical vibratory energy which operates at frequencies beyond audible sound, or 18,000 Hz (18,000 Hz being the upper threshold of the normal human hearing range). Four basic frequencies are generally used; 15,000 Hz, 20,000 Hz, 30,000 Hz, and 40,000 Hz, depending on the application. Selection is based upon the required power levels, the amplitude of vibration required and the size of the ultrasonic tool to be used. Frequency is important because it directly affects the power and amplitude available and the tool size. It is easier to generate and control high power levels at the lower frequency. Also, ultrasonic tools are resonant members whose size is inversely proportional to their operating frequency. The generation of ultrasonic energy starts with conversion of conventional 50 or 60 Hz electrical power to 15,000, 20,000, 30,000 or 40,000 Hz electrical energy by a solid state power supply.
Ultrasonic welding can be used in a wide variety of applications, including in connection with parts made from a number of materials and sizes. Moreover, such ultrasonic welding can be used in conjunction with a wide variety of automation. Currently, there is a growing desire to further automate the ultrasonic welding process and to this end attempts have been made to use complex imaging systems to detect the presence of a part to be welded. These imaging systems may include optical detectors and processing equipment to visually confirm a welding arrangement. As such, the imaging system is typically mounted to at an angle relative to the longitudinal axis of an ultrasonic welding horn. In this manner, the imaging system can detect the desired part and provide feedback for processing.
However, as the parts to be welded become larger, the size of the ultrasonic welding horn become larger, or the available space become more limited, the use of an off-axis detecting system may not provide sufficient operational benefits. Moreover, the complexity and cost of such imaging systems may be disadvantageous for most application. Still further, such imaging systems often fail to provide reliable operation and function. Accordingly, there exists a need in the relevant art to provide a simplified sensor system for use in ultrasonic welding applications.